Chinese police have arrested 108 Internet ball gamblers and confiscated 18 billion yuan ($2.9 billion) in illegal assets during the 2014 FIFA World Cup, held in Brazil from June 12 to July 13, the Ministry of Public Security said on Sunday.

Police also smashed a number of major Internet gambling rings during the World Cup, the ministry said.

"Most of the servers involving online soccer gambling were located overseas, and the foreign suspects colluded with their domestic counterparts to operate the criminal ring," said Zhang Hongqiang, press officer for the ministry.

He said the criminals have opened up many gambling games and sections on an overseas website to attract a large number of gamblers to make a bet, and they have received huge illegal gains through exacting commissions and "super membership" fees.

One typical case occurred on July 4, when the ministry directed public security organs across eight provinces, including Jiangsu, Guangdong, Fujian and Gansu, to conduct a unified action and smash a major transnational criminal Internet ball gambling ring.

Police arrested 17 main suspects and agents from the Philippines and China, and they seized and froze 30 million yuan in illegal funds, according to the ministry.

The operation dated back to May, when Jiangsu police found during a routine investigation that one overseas gambling website developed Chinese agents and organised ball gambling activities across the country, according to the ministry.

Jiangsu police reported this to the ministry, and the ministry immediately set up a special investigative team. It also instructed police agencies from seven other provinces to investigate further.

Police found during the investigation that the website server was based in the Philippines, and the banker, a Filipino, colluded with two Chinese operators to illegally open many gambling sections on the website and attract a large number of suspects to engage in gambling, the ministry said.

The ministry said the criminal gang behind the website received more than 200 million yuan in illegal funds through commissions and membership fees.

Earlier this year, the ministry initiated a special campaign to combat gambling activities, especially online sports gambling during the World Cup. The campaign will continue through the end of the year.

According to the ministry, police have uncovered 7,267 criminal cases since January that involved opening casinos and getting together for gambling, and they have arrested 23,000 suspects.

The ministry said it will pay attention to combating the organisers and operators involved in gambling crimes. Local police will reward the public for providing valuable tips, while intensifying supervision of the Internet to get timely intelligence, it said.

Because most of the website servers for gambling activities are located overseas, the key is "to use technical means and enhance law enforcement cooperation with relevant countries to strengthen intelligence collection and analysis", said Li Wei, a lawyer and member of the Beijing Lawyers Association.

Additionally, authorities should enhance cooperation with financial regulators and banking systems to tighten their supervision and prevent a large quantity of funds from being transferred abroad through illegal channels, such as money laundering and underground banking, Li said.